Micro device arrangement in donor  substrate

ABSTRACT

This disclosure is related to arranging micro devices in the donor substrate by either patterning or population so that there is no interfering with non-receiving pads and the non-interfering area in the donor substrate is maximized. This enables the transfer of micro devices to a receiver substrate with fewer steps.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a divisional of, and claims priority from U.S.application Ser. No. 15/724,320 filed on Oct. 4, 2017, which claimspriority to and the benefit of U.S. Provisional Patent Application Ser.No. 62/403,741, filed Oct. 4, 2016, U.S. Provisional Patent ApplicationSer. No. 62/426,353, filed Nov. 25, 2016, U.S. Provisional PatentApplication Ser. No. 62/473,671, filed Mar. 20, 2017, U.S. ProvisionalPatent Application Ser. No. 62/482,899, filed Apr. 7, 2017, and U.S.Provisional Patent Application Ser. No. 62/515,185 filed Jun. 5, 2017,each of which is hereby incorporated by reference herein in theirentirety.

TECHNICAL FIELD

The present disclosure relates to a system for transferring microdevices onto a receiver substrate, and in particular to the patterningof micro devices on a donor substrate, and the landing area on areceiver substrate to increase the efficiency of transfer process.

BACKGROUND

Several different selective transfer processes have already beendeveloped for micro devices. However, if the receiver substrate requiresdifferent micro devices that are part of different donor substrates, theextra devices on the other donor substrates may interfere with thelocations (pads) assigned to other types of micro devices on thereceiver substrate.

An object of the present invention is to overcome the shortcomings ofthe prior art by providing a particular patterning of devices on thedonor substrate to avoid interference with pads on the receiversubstrate destined for other micro devices. Other inventions comprisepre-processing the devices on a donor substrate (cartridge substrate),preparing the landing area (or pads) on a receiver substrate,transferring the micro devices from the donor substrate to the receiversubstrate, and post processing to enable device functionality. Thepre-processing step may include patterning and adding bonding elements.The transfer process may involve bonding of a pre-selected array ofmicro devices to the receiver substrate followed by removing the donorsubstrate.

SUMMARY OF THE INVENTION

Accordingly, the present invention relates to a method of populating areceiver substrate, comprising:

-   -   a) providing a receiver substrate including a plurality of        pixels, each pixel including first pads for receiving a first        type of micro device and second pads for receiving a second type        of micro device;    -   b) providing a first donor substrate including a plurality of        the first type of micro devices arranged in arrays separated by        first interfering areas void of the first type of micro devices;    -   c) aligning a first group of the first type of micro devices on        the first donor substrate with a first group of the first pads        on the receiver substrate, whereby the first interfering areas        of the first donor substrate overlap the second pads to prevent        interference with the second pads by the first type of micro        devices;    -   d) transferring the first group of the first type of micro        devices from the first donor substrate to the first group of the        first pads of the receiver substrate;    -   e) adjusting a relative position of the first donor substrate        and the receiver substrate to align a second group of the first        type of micro devices with a second group of the first pads on        the receiver substrate, whereby the first interfering areas of        the first donor substrate overlap the second pads to prevent        interference with the second pads by the first type of micro        devices; and    -   f) transferring the second group of the first type of micro        devices from the first donor substrate to the second group of        the first pads of the receiver substrate.

Another aspect of the present invention relates to a donor substratecomprising:

-   -   non-interfering areas including arrays of micro devices for        transfer to receiver pads on a receiver substrate; and    -   interfering areas comprising rows or columns of void areas for        overlapping non-receiving pads on the receiver substrate to        prevent micro devices on the donor substrate from interfering        with non-receiving pads during transfer of microdevices to the        receiving pads.

Another feature of the present invention provides a method of arrangingmicro devices on a donor substrate to avoid interference withnon-receiving pads on a receiver substrate during transfer of microdevices from the donor substrate to receiving pads on the receiversubstrate, comprising:

-   -   a) determining interfering areas on the donor substrate by        -   i) determining areas on the donor substrate that overlap            non-receiving pads on the receiver substrate during transfer            of a first micro device to a first receiving pad on the            receiver substrate; and        -   ii) determining areas on the donor substrate that will not            overlap non-receiving pads after offsetting at least one of            the donor or the receiver substrate relative to the other to            align at least a second micro device with a second receiving            pad on the receiver substrate or another receiver substrate            after the first micro device has been transferred to the            receiver substrate; and    -   b) arranging micro devices on the donor substrate in        non-interfering areas other than the interfering areas.

Another aspect of the present invention relates to a method ofpopulating a receiver substrate, comprising:

-   -   a) providing a receiver substrate including a plurality of        pixels, each pixel including first pads for receiving a first        type of micro device and second pads for receiving a second type        of micro device;    -   b) providing a first donor cartridge substrate including a        plurality of the first type of micro devices arranged in arrays,        and a plurality of the second type of micro devices arranged in        arrays, interleaved with the arrays of the first types of micro        device separated by a first interfering area void of the first        or second types of micro devices;    -   c) aligning a first group of the first types of micro devices        and a first group of the second type of micro devices on the        first donor cartridge substrate with a first group of the first        pads and a second group of second pads, respectively, on the        receiver substrate, whereby the first interfering area of the        first donor cartridge substrate overlap an area caused by a        difference in pitch between the pads and the pixels;    -   d) transferring the first group of the first and second types of        micro devices from the first donor cartridge substrate to the        first group of the first and second pads of the receiver        substrate;    -   e) adjusting a relative position of the first donor cartridge        substrate and the receiver substrate to align a second group of        the first and second types of micro devices with a second group        of the first and second pads on the receiver substrate, whereby        the first interfering areas of the first donor substrate overlap        an area caused by a difference in pitch between the pads and the        pixels; and    -   f) transferring the second group of the first and second types        of micro devices from the first donor substrate to the second        group of the first and second pads of the receiver substrate.

According to one embodiment, a method of populating a receiver substratemay be provided. The method may comprising the steps of: preparing aplurality of microdevices on one or more donor substrates, transferringthe plurality of microdevices form the one or more donor substrates to afirst cartridge substrate, the plurality of microdevices are arranged inarrays, separated by an interfering area in between, on the firstcartridge substrate, selecting one or more transferable sets of microdevices in the first cartridge substrate, identifying a number ofdefective microdevices in each transferable set of micro devices andcorrecting the defective microdevices prior to transfer, aligning andtransferring the selected micro devices on the first cartridge substrateto corresponding contact pads on a first receiver substrate; anddetermining if the first receiver substrate is fully populated withmicrodevices;

-   -   i) in response to determining that the first receiver substrate        is fully populated, proceeding to a second receiver substrate        and repeating steps c) to e),    -   ii) in response to determining that the first receiver substrate        is not fully populated, determining whether the first cartridge        substrate 1) has enough microdevices to continue transferring        microdevices to the first receiver substrate or 2) has not        enough microdevices to continue transferring microdevices to the        first receiver substrate;    -   iii) in response to determining that the first cartridge        substrate has enough microdevices, selecting another        transferable set of micro devices in the first cartridge        substrate and repeating steps d) to e); else in response to        determining that the first cartridge substrate has not enough        microdevices, selecting a second cartridge substrate and        repeating steps b) to f).

According to another embodiment, a method of transferring a plurality ofmicrodevices into a system substrate may be provided. The methodcomprising: arranging the plurality of microdevices in arrays separatedby an interfering area in between a cartridge substrate, selecting oneor more transferable sets of microdevices in the cartridge substrate,identifying a number of defective micro devices in each transferable setof micro devices, correcting the defective microdevices if a sum of anumber of the identified defective microdevices is more than a thresholdvalue; and aligning and transferring the selected micro devices on thecartridge substrate to corresponding contact pads on the receiversubstrate.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in greater detail with reference to theaccompanying drawings which represent preferred embodiments thereof,wherein:

FIG. 1 illustrates an example of a micro device arrangement in a donorsubstrate.

FIG. 2 illustrates an example of a receiver substrate pixel with threedifferent sub pixels.

FIG. 3A illustrates an embodiment of a donor substrate arranged intointerference and non-interference areas based on the receiver substrate.

FIG. 3B illustrates another embodiment of a donor substrate arrangedinto interference and non-interference areas based on the receiversubstrate.

FIG. 4 illustrates an embodiment using a taller pad associated with oneof the microdevices to improve the non-interfering area.

FIG. 5 illustrates a cluster pad embodiment to improve thenon-interfering area.

FIG. 6A illustrates an embodiment of a donor substrate with anon-interfering area associated with the pads at the edge of clusterpads.

FIG. 6B illustrates a donor substrate embodiment with a non-interferingarea associated with the inside pads of the cluster.

FIG. 7A illustrates an example of a donor substrate and a receiversubstrate with cluster pads.

FIG. 7B illustrates another example of a donor substrate and a receiversubstrate with cluster pads.

FIG. 8 illustrates an example of a receiver substrate with pads in thepixel arranged in two directions.

FIG. 9A illustrates an embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the pixel.

FIG. 9B illustrates another embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the pixel.

FIG. 9C illustrates another embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the pixel.

FIG. 9D illustrates another embodiment of a donor substrate withnon-interfering area associated with the one of the pads in the pixel.

FIG. 10 illustrates an embodiment with cluster pads to improve thenon-interfering area for the pixel pads arranged in two directions.

FIG. 11A illustrates an embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the cluster.

FIG. 11B illustrates another embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the cluster.

FIG. 11C illustrates another embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the cluster.

FIG. 12A illustrates an example of a donor substrate and a receiversubstrate with cluster pads arranged in two directions.

FIG. 12B illustrates an example of a donor substrate and a receiversubstrate with cluster pads arranged in two directions.

FIG. 12C illustrates an example of a donor substrate and a receiversubstrate with cluster pads arranged in two directions.

FIG. 12D illustrates an example of a donor substrate and a receiversubstrate with cluster pads arranged in two directions.

FIG. 13A illustrates an embodiment of a pad cluster in a receiversubstrate and a donor substrate with a non-interfering area associatedwith reference to the one of the pads in the cluster.

FIG. 13B illustrates another embodiment of a donor substrate with anon-interfering area associated with the one of the pads in the cluster.

FIG. 14A illustrates an example of a donor substrate and a receiversubstrate with cluster pads arranged in two directions.

FIG. 14B illustrates an example of a donor substrate and a receiversubstrate with cluster pads arranged in two directions.

FIG. 15A illustrates an example of a donor (cartridge) substrate withdifferent types of micro devices.

FIG. 15B is a flow chart of the process of the present invention.

FIG. 15C is a flow chart of the micro device mounting process of thepresent invention.

FIG. 16 illustrates an example of a donor (cartridge) substrate withdifferent types of micro devices.

FIG. 17 illustrates an example of a donor substrate for the same type ofmicro devices, but a different pitch between sets of micro devices.

FIG. 18 illustrates an example of a donor substrate with non-uniformityof output across a block of micro devices.

FIG. 19 illustrates an example of a receiver substrate withnon-uniformity of output across a plurality of block of micro devices.

FIG. 20 illustrates an example of a receiver substrate with skewedblocks of micro devices.

FIG. 21 illustrates an example of a receiver substrate with flippedblocks of micro devices.

FIG. 22 illustrates an example of a receiver substrate with flipped andalternating blocks of micro devices.

FIG. 23 illustrates an example of a donor substrate with two differentblocks of micro devices.

FIG. 24 illustrates an example of a receiver substrate with skewedblocks of different micro devices.

FIG. 25A illustrates an example of a donor substrate with threedifferent types of blocks of micro devices.

FIG. 25B illustrates an example of populating a cartridge from differentblocks to eliminate the non-uniformity found in any one block.

FIG. 26 illustrates an example of a cartridge substrate with a pluralityof different types of blocks of micro devices.

FIG. 27 illustrates an example of a cartridge substrate with a pluralityof different types of offset blocks of micro devices.

DETAILED DESCRIPTION

While the present teachings are described in conjunction with variousembodiments and examples, it is not intended that the present teachingsbe limited to such embodiments. On the contrary, the present teachingsencompass various alternatives and equivalents, as will be appreciatedby those of skill in the art.

In this disclosure, a pad on a receiver substrate refers to a designatedarea on the receiver substrate where a micro device has been or will betransferred from a donor substrate. The pads could be conductive toprovide a connection between the micro device and a pixel circuit or theconnections to the pixel circuits may be underneath the pad or on theside of the pad. The pad may have some form of bonding materials to holdthe micro device permanently. The pad may be a multi-layer stack tooffer a more mechanically stable structure, and also to provide betterfunctionality, such as bonding and conductivity capability.

The pads in this description may provide at least one of an electricalconnection, a mechanical connection, and a defined area for transferringmicro devices. The shapes of the pads used in the illustratedembodiments are for the purpose of illustration only, and the pads mayhave any arbitrary shape. The position of the pads with respect to thepixels may be changed without any effect on the embodiments. Theorientation of the group of pads in the pixel may be changed. Forexample, they may be rotated, shifted or moved to different positions.The pads may have a complex structure comprising different conductive,semiconductor and dielectric layers. The pads may be positioned on topof other structures, such as transistors, in the receiver substrate.Also, the pads may be beside other structures on the receiversubstrates.

The shape of the micro devices used in the embodiments are for purposeof illustration, and the micro devices may have different shapes. Themicro devices may have one or more pads on the side that will contactthe receiver substrate. The pads may provide mechanical or electricalconnection or a combination of both.

In one embodiment, a method of arranging micro devices in the donorsubstrate is described that is used to transfer micro devices to thereceiver substrate. In the donor substrate, micro devices are arrangedin relation to the pixel area, and within the area associated with thepixel the micro devices may have a pitch that is smaller than the pixelpitch.

In this arrangement, the pitch between the micro devices at the boundaryof two pixels may be different from the pitch of micro devices withinthe pixel.

In this case, there are more micro devices on the donor substrate thanintended/wanted pads in the receiver substrate associated with the donorsubstrate area. Therefore, the micro devices may interfere with otherunwanted/unintended pads in the receiver substrate. Several embodimentsin this document are described to define interfering areas of the donorsubstrate to either remove or not populate micro devices in those areas.This embodiment may be used for different micro device arrangements inthe donor substrate.

In another embodiment, a method of arranging micro devices described ina donor substrate to avoid interference with unwanted pads, includes

-   -   a) defining interfering areas or non-interfering areas where:        -   1) the non-interfering areas are spaces in the donor            substrate that are not covered by other unwanted pads during            micro device transfer to receiver substrate, i.e. the            interfering areas are covered by unwanted pads, OR        -   2) will not be covered by pads after offsetting the donor or            receiver substrate in a certain direction to align at least            one micro device with a wanted pad in the receiver substrate            after at least one micro device different from said micro            device is transferred to a pad different from the said pad            in the receiver substrate, i.e. the interfering areas will            be covered by pads in subsequent steps; and    -   b) arranging micro devices in the non-interfering areas of the        donor substrate.

In the receiver substrate described above, one pad on the receiversubstrate may have a taller structure, and the micro device associatedwith the pad may have a shorter structure. Thus, there will be nointerfering area for this pad.

To increase the non-interfering area, one embodiment comprises a methodof arranging the pads associated with the micro device transfer positionin the receiver substrate into clusters, wherein within said clustersthe pad pitch is smaller than the sub-pixel pitch.

In case of cluster pads, a donor substrate for a pad at the edge of acluster may be arranged in such way that interfering and non-interferingareas are similar to the pixel area where the width of the interferingarea is the same as the distance of the other pads from the pad.

In case of a cluster, a donor substrate for a pad inside of the clustermay be arranged, whereby interfering and non-interfering areas aresimilar to the pixel area, and the interfering areas are defined by:

-   -   a) Finding the distance between the pad and the edge of the        cluster;    -   b) Picking one micro device as a reference device on the donor        substrate;    -   c) Defining the interfering area from the micro device on both        sides similar to the distance of the associated pads to the edge        of the cluster.

The pattern of interfering and non-interfering areas, defined by an areaassociated with a pixel on the donor substrate, may be repeated on thedonor substrate similar to the pixel pitch.

In the remaining area of the donor substrate, patterned (arranged) forthe middle pad, associated with each pixel, a column (or row) of microdevices is between interfering areas whose width is larger than theminimum distance of the middle micro device from the edge of saidcluster.

In one embodiment to maximize the non-interfering area, the pad pitchwithin the cluster may be the same as the micro device pitch in thedonor substrate.

In another embodiment to maximize the non-interfering area, the pads maybe arranged in a two-dimensional cluster. The pads in the cluster may bealigned with at least another pad.

In one embodiment, a donor substrate for the pads may be aligned withother pads in two directions, creating diagonal interfering areas withreference to the pad cluster orientations. The area may contain otherpads and the remaining area associated with a pixel is non-interfering,in which micro device may exist.

In another embodiment, a donor substrate for the pads may be alignedwith pads in only one direction, which has the interfering area as:

One row including other pads if the said pad is aligned vertically withthe other pads, OR

One column if the said pad is aligned horizontally with another pad.

Whereby, the remaining area associated with a pixel is non-interferingin which a micro device can exist.

In this embodiment, donor substrate, and/or cartridge substrate are usedinterchangeably. The characteristics of the donor substrate can beapplied to the cartridge and vice versa.

FIG. 1 illustrates a donor substrate 150, in which there are more microdevices 160 than associated pads in a receiver substrate, e.g. see FIGS.2 and 3. In this case, the micro devices 160 may have a pitch 170smaller than a pixel pitch of the receiver substrate in an area or block130 of the donor substrate associated with the pixels. Also, as thepixel pitch may not be a multiple of the micro device pitch 170, themicro device pitch 180 between two adjacent (vertically andhorizontally) pixel areas 130 and 140 may have a different pitch, e.g. avoid or interference area, to accommodate the difference between thepixel and micro device pitches.

In traditional pick and place, the micro devices 160 on the transferhead, e.g. donor substrate 150, are transferred one at a time or one rowat a time to a position on the receiver substrate. To populate the restof the receiver substrate or another receiver substrate, the transferhead needs to be repopulated or a new donor substrate 150 must be used.This process requires fast and accurate movement and precision alignmentevery time to avoid the interference of the micro devices 160 on thedonor substrate 150 with other micro devices 160 already on the receiversubstrate or other pads on the receiver substrate not destined toreceive that particular micro device 160. However, the present inventionenables more micro devices 160 to be disposed on the donor substrate 150than what is required to populate an equivalent area on the receiversubstrate, thereby minimizing repopulation steps. Accordingly, empty orvoid areas on the donor substrate 150 enable the donor substrate 150 (orreceiver substrate) to be offset during the transfer process to alignthe remaining set of micro devices 160 with corresponding locations inthe receiver substrate. The offset can be done independently, or it canbe part of moving the donor substrate 150 to the new location on thereceiver substrate or a new receiver substrate.

FIG. 2 illustrates a pixel structure in a receiver substrate 200. Anarray of pixels on the receiver substrate 200 may be made of differentorientations and combinations of this pixel structure. The pixelstructure comprises different micro devices and each micro device mayhave a different pixel circuit or pixel connections. The pads 204, 214,224 for each micro-device type are put in each designated subpixel area202, 212, 222, with a width of 208, 218 and 228, respectively, andrepeated in both x and y directions forming an array of pixels. In theillustrated embodiment, the receiver substrate 200 includes threedifferent pads 204, 214, 224 for three different micro devices at adistance of 216 and 226 apart. However, one can use any number ofdifferent micro devices. In one pixel array structure, the micro devicetypes (or subpixel type) only vary in one direction (one-directionalarray structure). In another array type, the micro devices can vary intwo or more directions (two-directional array). If the donor substrate150 for each device type has micro devices 160 in all areas, i.e. acompletely filled 2×2 array, the micro devices 160, in correspondingareas to the pads 204, 214 and 224 of the other micro device types, mayinterfere with the pads 204, 214 and 224 during the transfer process. Inone case, only the micro devices 160 in the area related to thecorresponding pads, e.g. 204, on the receiver substrate 200, remain onthe donor substrate 150. However, in this case the donor substrate 150needs to be replaced or refilled after each transfer, which can increasethe processing steps. Moreover, the micro device utilization may beaffected, if the reset of micro devices 160 cannot be used. In oneaspect of the invention, the donor substrate 150 for each micro device160 is divided into interfering and non-interfering areas. The microdevices 160 from the interfering areas of the donor substrate 150 areremoved or not populated. In one aspect of this invention, the microdevices 160 are arranged in a donor substrate 150 to avoid interferingwith unwanted pads, e.g. 214 and 224, where the method includes:

-   -   a) defining non-interfering areas as:        -   i) spaces in the donor substrate 150 that do not correspond            with, overlap or interfere with other unwanted pads 204,            214, 224 on the receiver substrate 200 during transfer of a            first set of the micro devices 160 to a first set of the            pads 204 on the receiver substrate 200; and        -   ii) spaces in the donor substrate 150 that do not correspond            with, overlap or interfere with the pads 204, 214 and 224            after offsetting the donor or the receiver substrates 150 or            200, respectively, in a certain direction to align a second            set of the micro device 160 with a second set of the wanted            pad 204, 214 and 224 in the receiver substrate 200 after at            least the first set of the micro devices 160 different from            the second set of the micro devices 160 is transferred to            the second set of pads 214 or 224 different from the first            set of pads 204 in the receiver substrate 200; and    -   b) arrange the micro devices 160 only in the non-interfering        areas of the donor substrate 150.

Alternatively, the method may include:

-   -   a) defining interfering areas as:        -   i) spaces in the donor substrate 150 that correspond with,            overlap or interfere with other unwanted pads 204, 214, 224            on the receiver substrate 200 during transfer of a first set            of the micro devices 160 to a first set of the pads 204 on            the receiver substrate 200; and        -   ii) spaces in the donor substrate 150 that correspond with,            overlap or interfere with the pads 204, 214 and 224 after            offsetting the donor or the receiver substrates 150 or 200,            respectively, in a certain direction to align a second set            of the micro device 160 with a second set of the wanted pad            204, 214 and 224 in the receiver substrate 200 or a            different receiver substrate after at least the first set of            the micro devices 160 different from the second set of the            micro devices 160 is transferred to the second set of pads            214 or 224 different from the first set of pads 204 in the            receiver substrate 200; and    -   b) arrange the micro devices 160 only in the non-interfering        areas of the donor substrate 150, but not the interfering areas.

In one way to define the non-interfering areas, the directions of anoffsetting donor substrate 150 (or the receiver substrate 200) inrelation to the receiver substrate 200 (or the donor substrate 150) aredefined. For example, after a first set of the micro devices 160 aretransferred from the donor substrate 150 to the first set of pads 204,the donor substrate 150 is offset horizontally and vertically. Aftertransferring the first set of micro devices 160 from the donor substrate150 to the receiver substrate 200, the donor substrate 150 is eitheroffset horizontally or vertically. The other set of micro devices 160may be aligned with other related pads 214 or 224, and transferred tothese pads on the receiver substrate 200 that can be the originalreceiver substrate 200 or a different one. The following procedure is anexemplary process that can be used to identify the interfering andnon-interfering area.

-   -   a) A first set of micro devices for transferring to the receiver        substrate is used as a reference.    -   b) From the reference micro devices, draw lines in parallel with        the offsetting direction.    -   c) Draw lines in the direction of offsets from the corresponding        pads for other type of micro devices in reference to the        reference pads on the donor substrate.    -   d) Identify the closest lines from the other types of micro        devices to the lines of the micro device on the donor substrate.    -   e) Draw a line between the selected lines and the micro device        line. This line has a similar distance from each of the micro        device line and selected lines.    -   f) The areas defined by the new lines and encompassing the micro        device are the non-interfering areas. The other areas are        defined as interfering areas.

FIG. 3A shows one example of defining non-interfering area 304-1 andinterfering area 304-2. The pixel area 330 includes both non-interferingand interfering areas 304-1 and 304-2, respectively. In this case, themicro devices are offset horizontally and vertically. As a result, thewidth w_(ni) of the non-interfering area 304-1 for each micro device ishalf of the sum of the distances w₁ and w₂, between the pad 304 314 forthat micro device and the other adjacent pads 314304, 324, respectively.In FIG. 3B, the devices are offset horizontally and diagonally. As aresult, the non-interfering area 304-1 has a slope similar to the slopeof a diagonal offset process. As can be seen in both cases, thenon-interfering area 304-1 is small compared to the interfering area304-2.

One solution to address this issue is to have one of the pads 414 tallerthan at least one of the other pads 404, 424. The micro device 414-Dwith the taller pad 414 may be the more expensive device or more used onthe receiver substrate 400. However, it can be any other device as well.In the illustrated embodiment, the other micro devices 404-D and 424-Dmay have a taller structure compared to the micro devices 414-Dassociated with the taller pads 414, whereby the resulting combinationof pad 414 and device 414-D heights are substantially the same as thoseof pad 404 and device 404-D. One method to achieve a taller device is tohave taller connection pads. The taller pad may be on either side of thedevice. FIG. 4 shows an exemplary receiver substrate 400 in which one ormore pads 414 are taller than the other pads 404, 424. In theillustrated embodiment, three different micro devices 404-D, 414-D,424-D are being transferred to the receiver substrate 400 from donorsubstrates 450-04, 450-14, 450-24, respectively. The micro devices 404-Dand 424-D, associated with the shorter pad structures 404 and 424, havetaller structures compared to the other micro device 414-D. The sametechnique can be applied to other combination of micro devices (more orless than three micro devices). Accordingly, the shorter micro devices414-D will not interfere with the shorter pads 404 and 424, and theinterfering area on the donor substrate 450-14 is minimal.

In another solution, the pads 504, 514 and 524 for different microdevices may be set in a cluster 540 close to each other, leaving a largearea or pitch between clusters. In one embodiment, the circuit or otherconnections associated with the pads 504, 514 and 524 may be defined bysub-pixel structures #1, #2 and #3 with widths 508, 518 and 528,respectively, for ease of implementation. In another embodiment, thecircuits and connections may have any other structure. The closer thepads 504, 514 and 524 are together, the larger the non-interfering area506 will be. In one case, the distance between two pads, e.g. 216 or226, can be equal to or smaller than ⅓ of the pixel pitch 530 for threedifferent micro devices (three different sub-pixels) on the donorsubstrate. For more or fewer sub-pixels (micro device types) similarlythe pads 504, 514 and 524 may be put closer together. In one embodiment,the distances 216 and 226 between the pads 504, 514 and 524 in thecluster 540 is similar to the micro device pitch on the donor orcartridge substrate. If the different micro devices have the same pitchon the donor substrates, the cluster pads 504, 514 and 524 will have thesame pitch. In another case, the distance between the pads 504, 514 and524 in the cluster 540 is a multiple (for example twice that) of thepitch of micro devices on the donor substrate. In another embodiment,the distance between the pads can be smaller than the pitch of microdevices on the donor substrate. FIG. 5 shows a receiver substrate withan example of pad clusters 540. These pads 504 514, 524 may be from thesub-pixels 502, 512, 526 in one pixel 530 or from different pixels. Thepads 504, 514, 524 may be in any position with reference to the pixel530. It is possible that the order and position of the pads 504, 514,524 are different for different pixels.

FIG. 6A shows the interfering area 604-1, and the non-interfering 604-2area for the pad 604 at the edge of the cluster 640. The same structurecan be used for the other pad 624 at the other side of the cluster 640.As can be seen the non-interfering areas 604-2 for the pads 604 and 624at the edge of the cluster 640 are larger compared to previous cases.For the pad 614 in the middle, the non-interfering area 614-1 andinterfering area 614-2 can be a stripe pattern as demonstrated in FIG.6B. Here, the width of the stripe is the same as the distance betweenthe middle pad 614 and the other pads 604 and 624. To define thenon-interfering areas, following steps can be used:

-   -   a) Find the distance between the pad 604 and the edge of the        cluster pad    -   b) Pick one micro device as a reference device in the donor        substrate    -   c) Interfering area is defined from the micro device to both        sides similar to the distance of the associated pads to the edge        of cluster.

The pattern of interfering and non-interfering areas defined by an areaassociated with a pixel in the donor substrate can be repeated in thedonor substrate similar to the pixel pitch. In the remaining areas ofthe donor substrate, patterned (arranged) for the middle pad, associatedwith each pixel, a column (or row) of micro devices is betweeninterfering areas whose width is larger than the minimum distance of themiddle micro device from the edge of said cluster. If the distancebetween the middle pad and the other pads is the same, the ratio ofinterfering area 614-2 to non-interfering area 614-1 may be the same.Similar to FIG. 3B, the interfering and non-interfering areas 614-2 and614-1 may have different shapes depending on the offsetting direction.Also, similar to FIG. 4, the middle pad can be taller and so in thiscase the non-interfering area for the middle micro device can be theentire donor substrate.

If the micro devices do not have a similar pitch, the distance betweenpads 604, 614 and 624 in the cluster 640 can be similar to any of thepitch of the micro devices or each pad 604, 614 and 624 may havedifferent distance from the other pads. To improve the non-interferingarea, the middle device may be the one with the larger pitch, wherebyusing taller pads can help to improve the interfering area.

FIG. 7A illustrates an embodiment in which pads 704, 714 and 724 in areceiver substrate 700 have the same pitch as micro devices 752 and 754in a donor substrate 750. The position of a pad cluster 740 may bedifferent with reference to the pixels 730 on the receiver substrate700. The size of the pads 704, 714 and 724 may be smaller than, similarto, or larger than the micro devices 752 and 754. The shape of the microdevices 752 and 754 and the pads 704, 714 and 724 may be any suitableshape and size. In this case, the micro devices 752 and 754 may beremoved (or nonpopulated) from the interfering area on the donorsubstrate 750 creating void areas on the donor substrate 750corresponding to current or future populated or unpopulated pads on thereceiver substrate 700 and any subsequent receive substrate, which arenot designated to receive one of the micro-devices from the currentdonor substrate 750.

FIG. 7A illustrates an embodiment for the edge pad 704 (similarstructure can be used for 724). In the illustrated embodiment, the donorsubstrate 750 includes arrays of micro-devices 752 separated by voidareas, each with at least a width substantially equal to the sum of thepitches of the adjacent pads, e.g. pad 704 to 714 and pad 714 to 724, ofthe pitch×N (the number of adjacent pads) for equally spaced pads. Theminimum distance for the void areas, i.e. the distance between arrays ofmicro devices 752 on the donor substrate 750, is the distance from oneside of the pad closest to the pad being filled, e.g. pad 714, to theopposite side of pad farthest from the pad being filled, e.g. pad 724.In other words, the area to cover the other pads 714 and 724 withoutinterfering therewith during a current or any future transfer steps. Thedonor substrate 750 may be comprised of columns and rows of microdevices 752 and 754, and include void areas defined by a number ofmissing columns or rows equal to the number of pads, e.g. 714 and 724,adjacent to the receiver pad, e.g. 704, on each side thereof. The numberof columns in each array is dependent upon the spacing between the pads704 and 724 in adjacent pixels 730. For example, the donor substrate 750for the pad 704, which includes two adjacent pads 714 and 724 to theright and none to the left, may include a void area with two missingcolumns of micro devices, if the pitch of the micro devices 752 and 754is the same as the pads 714 and 724. Alternatively, if the pitches aredifferent, then the void area may be at least the distance from the pad,e.g. pad 704, mounted to the far edge of the farthest pad, e.g. pad 724.

Some of the micro devices 754 may have already been transferred to thereceiver substrate 700, and the donor substrate 750 (or the receiversubstrate 700) is offset vertically and/or horizontally with referenceto the next receiver substrate 700 (or donor substrate 750), so thatanother micro device 754 is aligned with one of the bare pads 704 (padsto which no micro device is transferred). In this case, the empty spacecreated by transferring the micro device 754 will be a new empty areawhich will be on top of the pad 714, and the empty space that was on topof the pad 714 will be on top of the pad 724, when the receiversubstrate 700 (or donor substrate 750) is subsequently offset again. Assuch there will be no interference caused by the micro devices 752 and754 for the unwanted pads 714 and 724. One can finish all the microdevices in one column by offsetting vertically first and then moving tothe next column (for example after finishing column 2, it moving tocolumn 1). However other combinations of vertical and horizontaloffsetting can be used. The pixels 730 or the pad clusters 740 may be atan angle either vertically or horizontally. In this case, the rows orcolumns of micro devices will be tilted as well. In addition, the microdevices can be at an angle without the pads or pixels being at angles.In this case, the offsetting direction will be toward the angle of thecolumn or the row.

FIG. 7B shows a similar structure for a donor substrate 751, as above,but for the middle pad 714, which would be aligned with the receiversubstrate 700 before or after the donor substrate 750. In theillustrated embodiment, the arrays, e.g. 1×N array, of micro devices 753and 755 are separated by void areas each with a width substantiallyequal to the sum of the pitches of the adjacent pads, e.g. 704 and 724,e.g. the pitch×N (N=the number of adjacent pads) for equally spacedpads. The minimum distance for the void areas, i.e. the distance betweenarrays of micro devices 753 on the donor substrate 751, is the distancefrom one side of the pad closest to the pad being filled, e.g. pad 704or 724, to the opposite side of the pad farthest from the pad beingfilled, e.g. the same pad 704 or 724. In other words, the void areashave enough space, i.e. distance between arrays of micro devices 753 tocover the other pads 704 and 724 without interfering therewith duringcurrent or future transfer steps. Typically, the length of the voidareas is the full length of the donor substrate 751. For pad clusters740 of three pads 704, 714 and 724, the donor substrate 751 for themiddle pads 714 may include arrays of micro devices 753 laterallyseparated by twice the pitch of the pads, and vertically separated bythe pitch of the pads. The donor substrate 751 may be comprised ofcolumns and rows of micro devices 753 and 755, and include void areasdefined by a number of missing columns or rows equal to the number ofpads, e.g. 704 and 724, adjacent to the receiver pad, e.g. 714, on eachside thereof. The number of columns in each array is dependent upon thespacing between the pads 704 and 724 in adjacent pixels 730. Forexample, the donor substrate 751 for the receiver pad 714, whichincludes one adjacent pad 704 to the left, and one pad 724 to the right,may include a void area with one missing column of micro devices on eachside, if the pitch of the micro devices 753 and 755 is the same as thepads 714 and 724. Alternatively, if the pitches are different, then thevoid area may be at least the distance from the pad, e.g. pad 714,mounted to the far edge of the farthest pad, e.g. pad 704 or 724.

FIG. 8 illustrates another pixel orientation embodiment 850, in whichthe sub-pixels 802, 812 and 822 are distributed in two dimensions, e.g.horizontally and vertically. The pads 804, 814 and 824 are shown in eachcorresponding sub-pixel 802, 812 and 822 area. A horizontal distance 806is between the pads 804 and 824, a horizontal distance 816 is betweenpads 804 and 814, a horizontal distance 826 is between pads 824 and 814,and a vertical distance 836 is between pad 824 and pads 804 and 814. Thedistances 806, 816, 826, and 836 are used to define the interfering andnon-interfering areas. The sub-pixels 802, 812 and 822 may be aligned invertical and horizontal orientations (or diagonally). For example, pads814 and 824 may be aligned vertically and so horizontal distance 826 maybe zero.

FIGS. 9A-9D illustrate some examples for the interfering areas and thenon-interfering areas for different pads 904, 914 and 924. FIG. 9A isfor pad 904 based on horizontal and vertical offsetting of microdevices. In this case, the non-interfering areas 904-1 and interferingarea 904-2 may be a combination of boxes around or offset from the pads904, 914, 924. FIG. 9B shows another example of the non-interfering area904-1 and the interfering area 904-2 for pad 904. Here, the denominatorof the two non-interfering areas between pad 904 and 914 and pads 904and 924 is used as the non-interfering area for pad 904. FIG. 9C showshorizontal non-interfering area 924-1 and interfering area 924-2. Forpad 914, the most optimized case is based on diagonal offsetting. FIG.9D shows the diagonal strips for the non-interfering area 914-1 and theinterfering area 914-2. Other patterns also may be used with differentoffsetting direction. In this embodiment different pad heights, asdescribed in FIG. 4, may be used to improve the device utilization forsome of the pads.

FIG. 10 illustrates another embodiment of a cluster pad 1040, in whichthe pads 1004, 1014 and 1024 are in two dimensions. Similar to FIG. 5,the pads 1004, 1014 and 1024 may have a different pitch depending on thedifferent pitches of the micro devices on the donor substrate.

FIG. 11A illustrates a non-interfering area 1104-1, and an interferingarea 1104-2 for a pad 1104 at the edge of a cluster 1140. Thenon-interfering areas for the pads at the edge are larger than previouscases. FIG. 11B shows a non-interfering area 1124-1 and an interferingarea 1124-2 for a pad 1124. For the pad 1114 in the middle, anon-interfering area 1114-1 and an interfering area 1114-2 may be adiagonally striped pattern, as demonstrated in FIG. 11C. Here, the widthof the strip is the same as the distance, e.g. center to center or thediagonal pitch, between the middle pad 1114 and the other pads 1104 and1124. If the distance between the middle pad 1114 and the other pads1104 and 1124 is the same, the ratio of the interfering area 1114-2 tothe non-interfering area 1114-1 may be the same. Similar to FIG. 3B,here the two areas can have different shapes depending on the offsettingdirection. Also, similar to FIG. 4, the middle pad 1114 can be tallerand so in this case the non-interfering area 1114-1 for the middle microdevice 1114 may be the entire donor substrate.

FIGS. 12A to 12D illustrates an embodiment in which the pads 1204, 1214and 1224 in a receiver substrate 1200 have the same pitch as microdevices 1252 and 1254 in a donor substrate 1250. The position of a padcluster 1240 on the receiver substrate 1200 may be different inreference to the pixels 1230 on the donor substrate 1250. The size ofthe pads 1204, 1214 and 1224 may be smaller or similar or larger thanthe micro devices 1252 and 1254. The shape of the micro devices 1252 and1254, and the pads 1204, 1214 and 1224 may be any suitable shape andsize. In this embodiment, the micro devices 1252 and 1254 are removed(or nonpopulated) from the interfering area on the donor substrate 1250.

FIG. 12A illustrates an embodiment of a donor substrate 1250 for theedge pad 1204. Some of the micro devices 1254 may have already beentransferred to the receiver substrate 1200, and the donor substrate 1250(or receiver substrate 1200) is offset vertically and/or horizontallywith reference to the next receiver substrate 1200 (or the donorsubstrate 1250) so that another micro device 1254 is aligned with thebare pads 1204 on a subsequent receiver substrate 1200 (pads to which nomicro device has yet been transferred). In the illustrated embodiment, aplurality of arrays or blocks of micro devices 1252 and 1254 areprovided on the donor substrate 1250. Within each array of microdevices, the spacing or pitch of the micro devices may be consistent,e.g. a first predetermined pitch, and is ideally the same pitch orspacing as the pads 1204 and 1214. Each array of micro devices isseparated by a void, i.e. an interfering area defined by a distanceacross of at least N times the pitch or spacing between the pads or fromone side of the closest pad to the far side of the farthest pad, e.g.1204 or 1214, where N is the number of adjacent pads, e.g. 1204 or 1214.Typically, the length of the void areas is the full length of the donorsubstrate 1250. In this case, the empty spaces on the donor substrate1250 created by transferring the micro device 1254 may be a new emptyarea, which could be on top of other pads 1214, 1224 in subsequentreceiver substrates 1200. As such there will be no interference causedby the micro devices for the unwanted pads 1214, 1224. One can finishall the micro devices 1254 in one column by offsetting vertically firstand then moving to the next column (for example, after finishing column2, moving it to column 1). However, other combinations of vertical andhorizontal offsetting can be used. The pixels 1230 or the pad clusters1240 can be at an angle be either vertically or horizontally. In thiscase, the rows or columns of the micro devices will be tilted as well.In addition, the micro devices 1252 and 1254 may be at an angle withoutthe pads or pixels being at angles. In this case, the offsettingdirection will be toward the angle of the column or the row.

The donor substrate 1250 may be comprised of columns and rows of microdevices 1252 and 1254, and includes void areas defined by a number ofmissing columns or rows equal to the number of pads, e.g. 1214, adjacentto the receiver pad, e.g. 1204, on each side thereof. The number ofcolumns in each array is dependent upon the spacing between the pads1204 and 1214 in adjacent pixels 1230. For example, the donor substrate1250 for the pad 1204, which includes one adjacent pad 1214 (pad 1224 isthe same lateral distance) to the right and none to the left, mayinclude a void area with one missing column of micro devices, if thepitch of the micro devices 1252 and 1254 is the same as the pads 1204and 1214. Alternatively, if the pitches are different, then the voidarea may be at least the distance from the pad, e.g. pad 1204, beingmounted to the far edge of the farthest pad, e.g. pad 1214.

FIG. 12B shows a similar structure for the donor substrate 1260, as inFIG. 12A, for the middle pad 1224 on the receiver substrate 1200.However, the interfering area with no micro device extends horizontallyacross the donor substrate 1260 to avoid interfering with pads 1204 and1214. As above, each donor substrate 1260 includes a plurality of arraysor blocks of micro devices 1253 and 1255. Within each array of microdevices, the spacing or pitch of the micro devices may be the same, e.g.a first predetermined pitch, ideally the same pitch or spacing as thepads 1204 and 1214, but may have a larger or smaller pitch. Each arrayof micro devices 1253 is separated by a void, i.e. an interfering area,of N times the pitch or spacing between the pads from one side of theclosest pad to the far side of the farthest pad, e.g. 1204 or 1214,where N is the number of adjacent pads, e.g. 1204 and 1214. Typically,the length of the void areas is the full length or width of the donorsubstrate 1260. The donor substrate 1260 for the middle pad 1224 ismoved laterally, i.e. perpendicular to the donor substrate 1250 for thepad 1204, for subsequent receiver substrates 1200.

FIG. 12C shows the donor substrate 1270 for the middle pad 1214. Here,the interfering area is diagonal, e.g. at an acute angle, relative tothe sides of the donor substrate 1270, and offsetting of the donorsubstrate 1270 (or receiver substrate 1200) for subsequent receiversubstrates 1200 (or donor substrates 1270) is done diagonally orvertically and horizontally. The donor substrate 1270 may be comprisedof columns and rows of micro devices 1257 and 1259, and include voidareas defined by a number of missing columns or rows equal to the numberof pads, e.g. 1204 and 1224, adjacent to the receiver pad, e.g. 1214, oneach side thereof. The number of columns in each array is dependent uponthe spacing between the pads 1214 and 1204 in adjacent pixels 1230. Forexample, the donor substrate 1270 for the pad 1214, which includes oneadjacent pad 1204 to the left, and one pad 1224 below (both are the samelateral distance diagonally) and none to the right, may include a voidarea with one missing diagonal column of micro devices, if the pitch ofthe micro devices 1257 and 1259 is the same as the pads 1214 and 1224.Alternatively, if the pitches are different, then the void area may beat least the distance from the pad, e.g. pad 1214, mounted to the faredge of the farthest pad, e.g. pad 1224.

FIG. 12D illustrates a donor substrate 1280, which has a similarstructure to the donor substrate 1260 for transferring to the pad 1214,but with a slightly different arrangement for the micro devices 1257 and1259 to maximize the transfer. The voids in the donor substrate 1270 areparallel (or perpendicular) to the sides of the donor substrate 1270,but the donor substrate 1270 is rotated, e.g. 45°, relative to thereceiver substrate 1200.

FIG. 13A shows a non-interfering area 1304-1, and an interfering area1304-2 for the pad 1304 at the edge of the cluster 1340 for a pixelwidth 1350 corresponding to a void area on a donor substrate. As seen,the non-interfering areas 1304-1 for the pads at the edge are largerthan previous cases. The same pattern may be used for the pad 1314. Forthe pad 1324 in the middle, the non-interfering area 1324-2 andinterfering area 1324-1 can be vertical stripe pattern as demonstratedin FIG. 13B. Here, the width of the non-interfering area 1324-2 is thesame as the distance between the middle pad 1314 and the other pads1304, 1324 in the other pixel. If the distance between the middle padand the other pads is the same, the ratio of interfering area 1324-1 2to non-interfering area 1324-2 1 may be the same. Similar to FIG. 3B,here the interfering and non-interfering areas 1324-1 2 and 1324-2 1 mayhave different shapes depending on the offsetting direction. Also,similar to FIG. 4, one of the pads may be taller and so in this case thenon-interfering area for the middle micro device may be the entire donorsubstrate.

FIGS. 14A and 14B illustrate an embodiment in which pads 1404, 1414 and1424 in a receiver substrate 1400 have the same pitch as micro devicesin donor substrates 1450 and 1460. The position of a pad cluster 1440may be different with reference to the pixels 1430. The size of pads1404, 1414 and 1424 may be smaller or similar or larger than the microdevices 1452, 1454, 1455 and 1457. The shape of the micro devices 1452,1454, 1455 ad 1457 and the pads 1404, 1414 and 1424 may be any suitablesize or shape. In this case, the micro devices 1452, 1454, 1455 and 1457may be removed (or nonpopulated) from the interfering area on the donorsubstrates 1450 and 1460.

FIG. 14A illustrates an embodiment of a donor substrate 1450 for theedge pad 1404. Some of the micro devices 1454 may already have beentransferred to the receiver substrate 1400, and the donor substrate 1450(or receiver substrate 1400) is offset vertically and/or horizontallywith reference to the next receiver substrate 1400 (or the donorsubstrate 1450) so that another micro device 1452 is aligned with one ofthe bare pads 1404 (pads to which no micro device has been yettransferred). In the illustrated embodiment, a plurality of arrays ofmicro devices 1452 and 1454 are provided on the donor substrate 1450.Within each array of micro devices, the spacing or pitch of the microdevices laterally and vertically may be the same, e.g. a firstpredetermined pitch, ideally the same pitch or spacing as the pads 1404and 1414. Each array of micro devices is separated by a void, i.e. aninterfering area, of N times the pitch of the pads or a spacing betweenthe pads or the lateral or vertical distance from one side of theclosest pad to the far side of the farthest pad, e.g. 1414 and 1424,where N is the number of laterally or vertically adjacent pads, e.g. twoin this case 1414 and 1424. Typically, the length of the void areas isthe full length of the donor substrate 1450.

In this case, the empty spaces created by transferring the micro device1454 will be a new empty area which will be on top of other pads 1414and 1424. As such there will be no interference caused by the microdevices for the unwanted pads 1414 and 1424. One can finish all themicro devices in one column by offsetting vertically first and thenmoving to the next column (for example, after finishing column 2, movingto column 1). However other combinations of vertical and horizontaloffsetting may be used. The pixels 1430 or the pad clusters 1440 may beat an angle to each other, either vertically or horizontally. In thiscase, the rows or columns of the micro device may be tilted as well. Inaddition, the micro devices may be at an angle without the pads orpixels being at angles. In this case, the offsetting direction will betoward the angle of the column or the row.

The donor substrate 1450 may be comprised of columns and rows of microdevices 1452 and 1454, and includes void areas defined by a number ofmissing columns or rows equal to the number of pads, e.g. 1414 and 1424,adjacent to the receiver pad, e.g. 1404, on each side thereof. Thenumber of columns in each array is dependent upon the spacing betweenthe pads 1424 and 1404 in adjacent pixels 1430. For example, the donorsubstrate 1450 for the receiver pad 1404, which includes two laterallyspaced adjacent pads 1414 and 1424 to the right (pad 1414 is equallyspaced from pads 1404 and 1424), and none to the left, may include avoid area with two missing columns of micro devices, if the pitch of themicro devices 1452 and 1454 is the same as the pads 1414 and 1424.Alternatively, if the pitches are different, then the void area may beat least the distance from the pad, e.g. pad 1404, being mounted to thefar edge of the farthest pad, e.g. pad 1424.

FIG. 14B illustrates a donor substrate 1460, similar to the structure inFIG. 14A, but for the middle pad 1414. However, the interfering areawith no micro devices 1455 and 1457 is a horizontal void, e.g. row, witha single column of micro devices missing, e.g. pads 1404 and 1424vertically spaced by one pitch distance from the receiver pad 1414.

FIG. 15A illustrates one example of a multi-type micro-device cartridge1800. The cartridge 1800 includes three different types, e.g. colors, ofmicro devices 1801, 1802, 1803, e.g. blue, green and red. However, anynumber and variety of different types of devices may be possible. Thedistances between the micro devices 1801, 1802 and 1803, i.e. x1, x2,x3, respectively, are related to the pitch of the landing areas in thereceiver substrate, e.g. receiver substrate 700 from FIGS. 7A and 7B.After an array or first set of micro devices 1805, which may be relatedto the pixel pitch in the receiver substrate, there may be a differentpitch x4, y2, i.e. a void area or interfering area, between adjacentsets 1805 and 1815 of micro devices 1801, 1802 and 1803. The separationor pitch is to compensates for a mismatch between the pixel pitch andthe micro device pitch (landing area pitch), and to ensure that microdevices on the donor or cartridge substrate 1800 do not interfere withpads, e.g. the horizontally and vertically adjacent cluster 740, orexisting micro devices on the receiver substrate, e.g. receiversubstrate 700. For example, the void area may be an area defined by atleast the distance from one side of an outer pad of the pixel to a farside of the outer pad at the opposite side of the pixel or at least thedistance of N times the pitch of the pads, where N is the number ofadjacent pads in the pixel. The length may be the entire length of thecartridge 1800. In this case, if pick and place is used to develop thecartridge 1800, the force elements may be in the form of columns thatcorresponds to the column of each micro device type or it can be aseparate element for each micro device.

With reference to FIG. 15B, during assembly, a first step 1821 includespreparing micro devices on the original donor substrates, e.g. donorsubstrates 750 or 1450. Then, in step 1822, the micro devices areprepared for separation from the donor substrates 750 or 1450. In step1823 the micro devices from one or more donor substrates, e.g. 750 and1450, are transferred onto the cartridge 1800, and arranged according tothe pixel arrangement on the receiver substrate, e.g. 700 or 1400. Thenext step 1824, which is optional, involves identifying micro deviceswith defects, and either correcting them in place, or removing them andreplacing them with an operating micro device in step 1825. Theidentification of defects may be conducted in the cartridge 1800 beforetransfer or on the receiver substrate 700 or 1400 after transfer ,orboth. Subsequently, or prior, to the identification and correction step1824, a plurality of groups of micro devices 1801, 1802 and 1803, whichmay form a pixel, from each array or set of micro devices 1805, 1810 and1815, may be mounted on the receiver substrate, e.g. receiver substrate700, simultaneously from the cartridge 1800, in step 1826.

With reference to FIG. 15C, the transfer step 1826 may be broken downinto a logical loop, in which the first step 18261 comprises loading orselecting a first cartridge 1800. The next step 18262 comprisesselecting a set of micro devices on the cartridge 1800 for transfer,preferably ones already tested for defects, and that comprise a numberof defects below a desired threshold value, e.g. less than 10%. Step18263 comprises aligning the selected micro devices on the cartridge1800, e.g. by moving or offsetting the cartridge 1800 or the receiversubstrate, e.g. receiver substrate 700, or both, relative to the otherinto alignment with a subsequent plurality of clusters of pads, e.g.cluster 740. The next step 18264 includes transferring the aligned microdevices on the cartridge 1800 to the pads on the receiver substrate,e.g. 700 or 1400. Step 18264 may be broken down into substeps including18264 a, in which the selected micro devices from the cartridge 1800 areconnected to the receiver substrate, e.g. 700 or 1400. Substep 18264 bcomprises turning on the micro devices to test their connection to thereceiver substrate, e.g. 700 or 1400. The test may be conducted bybiasing the micro devices through the cartridge 1800 and/or the receiversubstrate, e.g. 700 or 1400. If some of the micro devices are found tobe defective, step 18264 c includes adjusting one or more of the bondingparameters of the micro devices to correct the cause of the defect. Step18265 determines whether the receiver substrate, e.g. 700 or 1400, isfully populated. If yes, in step 18266, the process proceeds to a newreceiver substrate and the mounting process is repeated. If no, step18267 determines if the cartridge 1800 includes enough micro devices tocontinue with further transfers. If yes, the process returns to step18262 for the selection of the next set of micro devices to betransferred. If no, the process returns to step 18261 for selection ofanother cartridge 1800.

FIG. 16 illustrates another example of a multi-type micro-devicecartridge 1900. The cartridge 1900 includes three different types, e.g.colors, of micro devices 1901, 1902, 1903. The other area 1904 may bespare micro devices or a void area (interfering area). However, anynumber and variety of different types of device may be possible. Thedistances between micro devices x1, x2, x3 are related to the pitch ofthe landing areas in the receiver substrate, e.g. receiver substrate1200, in FIGS. 12A-12D. After an array or a first set of micro devices,which may be related to the pixel pitch in the receiver substrate, theremay be a different lateral and vertical pitch x4, y2, i.e. a void areaor interfering area, between laterally and vertically adjacent sets ofpixels. This pitch compensates for any mismatch between the pixel pitchand the micro device pitch (landing area pitch), and ensures that microdevices on the donor or cartridge substrate 1900 do not interfere withpads, e.g. the horizontally and vertically adjacent cluster 1240, orexisting micro devices on the receiver substrate, e.g. receiversubstrate 1200. For example, the void area may be an area defined by atleast the distance from one side of an outer pad of the pixel to a farside of the outer pad at the opposite side of the pixel or at least thedistance of N times the pitch of the pads, where N is the number ofadjacent (horizontally or vertically) pads in the pixel. The length maybe the entire length of the cartridge 1900. During assembly, a pluralityof groups of micro devices 1901, 1902 and 1903, which may form a pixel,from each array or set of micro devices, may be mounted on the receiversubstrate, e.g. receiver substrate 1200, simultaneously. Then thecartridge 1900 or the receiver substrate, e.g. receiver substrate 1200,or both are moved relative to the other into alignment with a subsequentplurality of clusters of pads, e.g. cluster 1240, and the mountingprocess is repeated, until the cartridge 1900 is empty or the receiversubstrate is filled. Another cartridge 1900 or receiver substrate isintroduced.

FIG. 17 illustrates one example of micro devices, e.g. 1801 or 1902,prepared on a donor substrate 1850 before transferring to multi-typemicro-device cartridge, e.g. 1800 or 1900. Here, one can use supportinglayers 1860, 1870 for individual device or for a group of devices. Here,the micro device pitch x1 can match the pitch in the cartridge 1800 or1900 or it can be multiple of cartridge pitch. As above the vertical andhorizontal array pitch y2 and x4 provide voids or interference areas toprevent interaction of the micro devices 1801 with pads on the receiversubstrate or undesired areas on the cartridge 1800 or 1900.

In all the structures above, it is possible to move the micro devicesfrom the first cartridge to a second one prior to using them inpopulating a substrate. Extra processing step can be done aftertransfer. or some of the processing steps can be divided between firstand secondary cartridge structure.

FIG. 18 illustrates an example of a block of microdevices 1482 on adonor substrate 1480, which may be any one of the aforementioned donorsubstrates described herein. As a result of manufacturing and materialflaws, the microdevices may have a gradual decrease or increase inoutput power, i.e. non-uniformity, across the donor substrate, asillustrated with darker to lighter coloring. Since the micro devices maybe transferred together in the block 1482 or one or more at a time insequence into the receiver substrate, the adjacent devices in thereceiver substrate gradually degrade in uniformity. However, a worseproblem may occur where a series of the blocks 1482 ends and the nextseries of blocks starts, e.g. along an intersection line 1484, which mayresult in an abrupt change as demonstrated in FIG. 19. The abrupt changemay result in visual artifact for optoelectronic devices, such asdisplays.

In order to solve the problem of non-uniformity, one embodiment,illustrated in FIG. 20, includes skewing or staggering the individualblocks 1482 with the ones below and above them in the display, so thatthe edge of the blocks are not sharp lines, i.e. eliminating theintersection 1484, and whereby the blocks of devices 1482 form a skewedpattern on the display. Therefore, the average impact of the sharptransition is reduced significantly. The skew may be random and may havedifferent profiles.

FIG. 21 illustrates another embodiment, in which the microdevices inadjacent blocks are flipped so that the devices with similar performanceare adjacent one another, e.g. the performance in a first block decreasefrom a first outer side to a first inner side, while the performance ofa second adjacent block increases from a second inner side, adjacent tothe first inner side to a second outer side, which may keep the changesvery smooth and eliminate the abrupt intersection 1484.

FIG. 22 illustrates an exemplary combination of flipping the devices,alternating the high and low performing devices at the inner sides, andskewing the edges to improve the average uniformity furthermore. In theillustrated example, the device performance alternates between high andlow in both directions, i.e. in adjacent horizontal blocks and inadjacent vertical blocks.

In one case, the performance of micro devices at the edges of the blocksare matched for adjacent transferred blocks (array) prior to thetransfer to the receiver substrate.

FIG. 23 illustrates using two or more blocks 1580 and 1582, to populatea block in the cartridge or receiver substrate 1590. Here also themethod of skewing or flipping can be used for further improving theaverage uniformity as demonstrated in FIG. 24. Also, a random orpredefined pattern may be used to populate the cartridge or receiversubstrate 1590 with micro devices from more than one block.

FIG. 25A illustrates samples with more than one blocks 1680, 1682 and1684, which may be from the same donor substrate or different donorsubstrates. FIG. 25B illustrates an example of populating a cartridge1690 from different blocks to eliminate the non-uniformity found in anyone block.

FIGS. 26 and 27 illustrate structures with multiple cartridges 1790. Theposition of the cartridges 1790 are chosen in a way to eliminateoverlapping the same area in the receiver substrate with cartridges withthe same micro-devices during different transfer cycles. In one case,the cartridge may be independent of the other cartridges, which meansseparate arms or controller is handling each cartridge independently. Inanother case, the alignment may be done independently, but the otheractions can be synchronized. In this case, the substrate may move tofacilitate the transfer after the alignment. In another case, thecartridges may move together to facilitate the transfer after thealignment. In another case, both may move to facilitate the transfer. Inanother case, the cartridges may be assembled in advanced. In this case,a frame or substrate can hold the assembled cartridges. The distance X3,Y3 between cartridges 1790 can be a multiple of the width X1, X2 orlength Y1, Y2 of the cartridge 1790. It can be a function of movingsteps to different direction. For example, X3=KX1+HX2, where K is themovement step to left (directly or indirectly) and H is the movementsteps to the right (directly or indirectly) for populating a substrate.The same can be used for distance between cartridges Y3 and the lengthof Y1 and Y2. As shown in FIG. 26, the cartridges may be aligned in oneor two direction. In another case, shown in FIG. 27, the cartridges maynot be aligned in at least one direction. Each cartridge 1790 may haveindependent control for applying pressure and temperature toward thesubstrate. Other arrangements are also possible depending on thedirection of movement between substrate and cartridges.

In another case, the cartridges 1790 may have different devices andtherefore populating different areas in the receiver substrate withdifferent devices. In this case, the relative position of the cartridges1790 and the receiver substrate changes after each transfer cycle topopulate a different area with all the required micro devices from thedifferent cartridges.

In another case, several arrays of cartridges 1790 are prepared. Here,after devices are transferred to the receiver substrate from a firstarray of cartridges, the receiver substrate is moved to the next arrayof micro devices to fill the remaining areas in the receiver substrateor receive different devices.

In another case, the cartridges 1790 may be on a curve surface andtherefore circular movement provides contact for transferring the microdevices into the substrate.

According to one embodiment, a method of populating a receiver substratemay be provided. The method may comprising the steps of: preparing aplurality of microdevices on one or more donor substrates, transferringthe plurality of microdevices form the one or more donor substrates to afirst cartridge substrate, the plurality of microdevices are arranged inarrays, separated by an interfering area in between, on the firstcartridge substrate, selecting at least one set of microdevices in thefirst cartridge substrate associated with a set of contact pads in thereceiver substrate, identifying a number of defective microdevices inthe at least one set of microdevices;, correcting the defectivemicrodevices if the number of defective microdevices in the set is morethan a set threshold value; and aligning and transferring the selectedset of microdevices on the first cartridge substrate to correspondingcontact pads on the receiver substrate.

According to another embodiment, wherein after transferring the selectedset of microdevices to the receiver substrate, if the receiver substrateis not fully populated, the method further comprising the steps of:determining whether the first cartridge substrate 1) has enoughmicrodevices to continue transferring microdevices to the receiversubstrate or 2) has not enough microdevices to continue transferringmicrodevices to the receiver substrate, in response to determining thatthe first cartridge substrate has enough microdevices, selecting anotherset of microdevices in the first cartridge substrate for transferring tothe receiver substrate; else in response to determining that the firstcartridge substrate has not enough microdevices, selecting a secondcartridge substrate.

According to one embodiment, the defective microdevices are removed ifthe number of the defective microdevices is more than the set thresholdvalue, the defective microdevices are repaired if the number of thedefective microdevices is less than the set threshold value and thedefective microdevices are replaced with spare microdevices on eachcartridge substrate if the number of the defective microdevices is lessthan the set threshold value.

According to some embodiments, the step of selecting one or more sets ofmicrodevices on the first cartridge substrate and the second cartridgesubstrate comprising: selecting one or more sets of microdevices,wherein number of defected microdevices in one or more sets ofmicrodevices is less than a threshold value; and transferring theselected set of microdevices to populate the system substrate.

According to another embodiment, the first cartridge substrate and thesecond cartridge substrate includes different types of the plurality ofmicrodevices. The different types of microdevices comprises one of: redcolor microdevices, blue color microdevices or green color microdevices.The plurality of microdevices of different types are arranged in arrayson each cartridge according to a type of microdevice.

According to yet another embodiment, the interfering area comprises oneof: spare microdevices or void areas.

According to some embodiments, the method may further comprising biasingthe microdevices through the receiver substrate to test a connectionbetween the transferred microdevices and the receiver substrate andadjusting one or more of the bonding parameters of the microdevices tocorrect the cause of the defective microdevices, wherein a distancebetween the plurality of microdevices on each cartridge substratedepends on a pitch of corresponding contact pads on the receiversubstrate.

According to another embodiment, rows of the micro devices from eachcartridge substrate are placed in a skewed arrangement on the receiversubstrate to reduce the effect of abrupt transitions caused bynon-uniformity of microdevices across each cartridge substrate.

According to one embodiment, laterally adjacent rows of the microdevices from different cartridge substrates are placed in a flippedarrangement on the receiver substrate with the high or low side of a rowfrom one of the donor substrates adjacent to a high side or low side,respectively, of an adjacent row of another donor substrate to reduceabrupt transitions caused by non-uniformity of micro devices across eachcartridge substrate.

According to further embodiments, vertically adjacent rows of microdevices from different cartridge substrates are placed in an alternatingarrangement with high sides vertically adjacent to low sides to reduceabrupt transitions caused by non-uniformity of micro devices across eachcartridge substrate.

According to another embodiment, a method of populating a receiversubstrate, the method comprising the steps of: preparing a plurality ofmicrodevices on one or more donor substrates, transferring the pluralityof microdevices form the one or more donor substrates to a cartridgesubstrate, the plurality of microdevices are arranged in arrays,selecting one or more sets of microdevices in the cartridge substratefor transferring to the receiver substrate, wherein a number ofdefective microdevices in the selected one or more sets of microdevicesis less than a set threshold value; and aligning and transferring theselected set of microdevices on the cartridge substrate to correspondingcontact pads on the receiver substrate.

According to one embodiment, the number defective microdevices areidentified and corrected before or after transferring to the receiversubstrate, the defective microdevices are corrected by one of:repairing, replacing or removing the defective microdevices in thecartridge substrate the defective microdevices are replaced with thespare microdevices on the cartridge substrate.

According to further embodiment, the cartridge substrate includesdifferent types of the plurality of microdevices, the different types ofmicrodevices comprises red color microdevices, blue color microdevicesor green color microdevices.

The foregoing description of one or more embodiments of the inventionhas been presented for the purposes of illustration and description. Itis not intended to be exhaustive or to limit the invention to theprecise form disclosed. Many modifications and variations are possiblein light of the above teaching. It is intended that the scope of theinvention be limited not by this detailed description, but rather by theclaims appended hereto.

We claim:
 1. A method of populating a receiver substrate, the methodcomprising the steps of: preparing a plurality of microdevices on one ormore donor substrates; transferring the plurality of microdevices formthe one or more donor substrates to a first cartridge substrate, theplurality of microdevices are arranged in arrays; selecting at least oneset of microdevices in the first cartridge substrate associated with aset of contact pads in the receiver substrate; identifying a number ofdefective microdevices in the at least one set of microdevices;correcting the defective microdevices if the number of defectivemicrodevices in the set is more than a set threshold value; and aligningand transferring the selected set of microdevices on the first cartridgesubstrate to corresponding contact pads on the receiver substrate. 2.The method of claim 1, wherein after transferring the selected set ofmicrodevices to the receiver substrate, if the receiver substrate is notfully populated, the method further comprising the steps of: determiningwhether the first cartridge substrate 1) has enough microdevices tocontinue transferring microdevices to the receiver substrate or 2) hasnot enough microdevices to continue transferring microdevices to thereceiver substrate, in response to determining that the first cartridgesubstrate has enough microdevices, selecting another set of microdevicesin the first cartridge substrate for transferring to the receiversubstrate; else in response to determining that the first cartridgesubstrate has not enough microdevices, selecting a second cartridgesubstrate.
 3. The method of claim 1, wherein the defective microdevicesare removed if the number of the defective microdevices is more than theset threshold value.
 4. The method of claim 1, wherein the defectivemicrodevices are repaired if the number of the defective microdevices isless than the set threshold value.
 5. The method of claim 1, wherein thedefective microdevices are replaced with spare microdevices on eachcartridge substrate if the number of the defective microdevices is lessthan the set threshold value.
 6. The method of claim 1, wherein the stepof selecting one or more sets of microdevices on the first cartridgesubstrate and the second cartridge substrate comprising: selecting oneor more sets of microdevices, wherein number of defected microdevices inone or more sets of microdevices is less than a threshold value; andtransferring the selected set of microdevices to populate the systemsubstrate.
 7. The method of claim 1, wherein the first cartridgesubstrate and the second cartridge substrate includes different types ofthe plurality of microdevices.
 8. The method of claim 7, wherein thedifferent types of microdevices comprises red color microdevices, bluecolor microdevices or green color microdevices.
 9. The method of claim1, wherein the different types of microdevices are arranged in arrays oneach cartridge according to a type of microdevice.
 10. The method ofclaim 1, further comprising: biasing the microdevices through thereceiver substrate to test a connection between the transferredmicrodevices and the receiver substrate.
 11. The method of claim 1,further comprising: adjusting one or more of the bonding parameters ofthe microdevices to correct the cause of the defective microdevices. 12.The method of claim 1, wherein a distance between the plurality ofmicrodevices on each cartridge substrate depends on a pitch ofcorresponding contact pads on the receiver substrate.
 13. The methodaccording to claim 1, wherein rows of the micro devices from eachcartridge substrate are placed in a skewed arrangement on the receiversubstrate to reduce the effect of abrupt transitions caused bynon-uniformity of microdevices across each cartridge substrate.
 14. Themethod according to claim 1, wherein laterally adjacent rows of themicro devices from different cartridge substrates are placed in aflipped arrangement on the receiver substrate with the high or low sideof a row from one of the donor substrates adjacent to a high side or lowside, respectively, of an adjacent row of another donor substrate toreduce abrupt transitions caused by non-uniformity of micro devicesacross each cartridge substrate.
 15. The method according to claim 1,wherein vertically adjacent rows of micro devices from differentcartridge substrates are placed in an alternating arrangement with highsides vertically adjacent to low sides to reduce abrupt transitionscaused by non-uniformity of micro devices across each cartridgesubstrate.
 16. A method of populating a receiver substrate, the methodcomprising the steps of: preparing a plurality of microdevices on one ormore donor substrates; transferring the plurality of microdevices formthe one or more donor substrates to a cartridge substrate, the pluralityof microdevices are arranged in arrays; selecting one or more sets ofmicrodevices in the cartridge substrate for transferring to the receiversubstrate, wherein a number of defective microdevices in the selectedone or more sets of microdevices is less than a set threshold value; andaligning and transferring the selected set of microdevices on thecartridge substrate to corresponding contact pads on the receiversubstrate.
 17. The method of claim 16, wherein the number defectivemicrodevices are identified and corrected before or after transferringto the receiver substrate.
 18. The method of claim 17, wherein thedefective microdevices are corrected by one of: repairing, replacing orremoving the defective microdevices in the cartridge substrate.
 19. Themethod of claim 18, wherein the defective microdevices are replaced withthe spare microdevices on the cartridge substrate.
 20. The method ofclaim 16, wherein the cartridge substrate includes different types ofthe plurality of microdevices, the different types of microdevicescomprises red color microdevices, blue color microdevices or green colormicrodevices.